‘We are both protected by the Emperor. My faith shields me.’

‘Like it protected these people here?’ said Guilliman. He gestured at a heap of greening bones pinned under the fallen roof.

Mathieu smiled. ‘Your father cannot be everywhere, my lord, and the faith of some is stronger than others. For the moment, your father protects me.’

‘Whether that is true or not,’ said Guilliman. ‘I would prefer it if you wore an environment suit. See, the Sisters and my Space Marines keep their helms sealed – even Maldovar Colquan and his Adeptus Custodes would not risk being in here without the correct filtration equipment. They are among the closest of all men to the Emperor, and made with great art. If they are cautious, so should you be.’

Very few men would ignore a suggestion like that from the primarch, but Frater Mathieu shook his head.

‘I will be well. I have been fighting all day, and I am untouched. I am protected.’ He walked around the exedra. He drew dangerously close to the cursed clock. He made the sign of the aquila, but showed no sign of being affected by the malevolence radiating palpably from it.

Guilliman scrutinised the priest carefully, waiting for signs of madness or disease. When Mathieu did not speak for some time, Guilliman’s hand shifted within the Hand of Dominion. He was close to sending the mental command via his battleplate’s nerve shunts that would bring it sparking into life. He relaxed when Mathieu knelt in the filth of the floor and bowed his head. There he prayed silently. The Sisters of Silence dipped their helms, as if in communion with him. Guilliman shared a glance with Colquan. The Custodian gave a small shrug that sent his ornate armour into a ripple of gold.

His prayer done, Mathieu stood and genuflected towards the ruined wooden effigy of his god, then he turned to the Emperor’s last loyal son.

‘Where do they find such hate?’ he asked. ‘What could make them want to become like this? They have made themselves monsters.’

The question brought a hard expression to Guilliman’s face. ‘Hatred is in the hearts of all men,’ the primarch said. ‘It is in my heart. I hate the Death Guard for abandoning reason and for what they have become. I hate my brothers for their betrayal. But I do not blame them. Most hate springs from fear, or shame, or despair. The traitors despair, I am sure. They must feel shame at what they have destroyed, and so they become more extreme in their hatred.’

‘You speak mercifully of the heretics,’ said Mathieu softly.